Do you find that from time to time you need to tackle a longer than normal climb? Not all of the world is made up of mountains and flat land. Those of us who deal with rollers and steep climbs, that make 4-5 minutes feel like an eternity, are faced with longer gradual climbs from time to time. You would think that all the short and steep stuff would prepare you for a long grinder. If it doesn’t try to break the climb into segments. Start the beginning of the climb like any other. Then scoot your but back in the saddle for a bit. Then move to the nose of the saddle and drive your knees up as if you are trying hit your handle bars. If you have more climbing shift up 2 gears and stand while climbing. If this didn’t get you to the top repeat one or more of these techniques until you do.